package 面试;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.atomic.AtomicStampedReference;

public class ABAdemo {

    static AtomicReference<Integer> atomicReference = new AtomicReference<>(100);
    static AtomicStampedReference<Integer> atomicStampedReference = new AtomicStampedReference<>(100, 1);

    public static void main(String[] args) {

        System.out.println("===============ABA问题的产生=================");

        new Thread(() -> {
            atomicReference.compareAndSet(100, 101);
            atomicReference.compareAndSet(101, 100);
        },"t1").start();

        new Thread(() -> {
            try {
                TimeUnit.SECONDS.sleep(1);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(atomicReference.compareAndSet(100, 2019) + "\t" + atomicReference.get());
        },"t2").start();
        try {TimeUnit.SECONDS.sleep(2);} catch (InterruptedException e) {e.printStackTrace(); }

        System.out.println("===============ABA问题的解决=================");

        new Thread(() -> {
            int stamp = atomicStampedReference.getStamp();
            System.out.println(Thread.currentThread().getName() + "\t第1次版本号" + stamp);
            //停一秒
            try {TimeUnit.SECONDS.sleep(1);} catch (InterruptedException e) {e.printStackTrace(); }
            atomicStampedReference.compareAndSet(100,101,atomicStampedReference.getStamp(), atomicStampedReference.getStamp()+1);
            System.out.println(Thread.currentThread().getName() + "\t第2次版本号" + atomicStampedReference.getStamp());
            atomicStampedReference.compareAndSet(101,100,atomicStampedReference.getStamp(), atomicStampedReference.getStamp()+1);
            System.out.println(Thread.currentThread().getName() + "\t第3次版本号" + atomicStampedReference.getStamp());
            },"t3").start();

        new Thread(() -> {
            int stamp = atomicStampedReference.getStamp();
            System.out.println(Thread.currentThread().getName() + "\t第1次版本号" + stamp);
            //停三秒
            try {TimeUnit.SECONDS.sleep(3);} catch (InterruptedException e) {e.printStackTrace(); }
            boolean result = atomicStampedReference.compareAndSet(100, 2019, stamp, stamp + 1);
            System.out.println(Thread.currentThread().getName() + "\t 修改成功否：" + result + "\t当前最新实际版本号：" + atomicStampedReference.getStamp());
            System.out.println(Thread.currentThread().getName() + "\t当前最新实际值：" + atomicStampedReference.getReference());
        },"t4").start();

    }
}
